toxic agents III

Question 1

factors that affect plant toxicity?

there are 4 factors!

Answer 1

• age of plant
• amount of sunlight
• quality of soil
• genetic variations/ differences

this affect the concentration and toxic effect of phytotoxins

Question 2

how castor bean inhibit protein synthesis?

ricin has both A and B chain

Answer 2

1. B chain help bind toxin to terminal galactose residue in glycoproteins and glycolipids in cell surface
2. ricin then enters via endocytosis and travel to endosomes
3. most ricin go back to cell surface via exocytosis/ degraded in lysosomes
4. some ricin enter GA, undergo retrigrade transport to ER -> cleaving of the A and B chain
5. ricin A chain translocate to cytosol -> inactivate ribosome by removing adenine of the 28S rRNA in 60s ribosomal subunit
6. inhibit translation -> will depurinate the adenine base
7. depurinated rRNA is unable to bind protein elongation factors, protein synthesis stops

can lead to cell death, can also mediate other cytotoxic effects

Question 3

toxicity mechanism of angel trumpet’s seeds

it contains atropine

Answer 3

in normal condition:
1. phospholipase C activates DAG (diacyglycerol)
2. DAG activate IP3 -> IP3 release Ca2+ from ER and cause muscle contraction
3.in case of atropine -> blocks the M1 activation -> inhibit muscle contraction -> dry mouth and constipation
4.atropine -> blocks M3 activation -> cause pupil dilation

Question 4

what is animal toxicity?

the role of animal’s venom

Answer 4

role:
- as offense, to capture and digest food
- as defense, to protect against predators

is very complex and contain many individual toxic compounds and very large and different proteins

Question 5

what do spider venom contains?

what is it composed of?

Answer 5

venom can produce neurotoxins that can paralyze or kill prey
venom is composed of:
- inorganic ions and salts
- free acids
- glucose-free amino acids
- biogenic amines and neurotransmitters
- polypeptide toxins

Question 6

toxicity mechanism of spider’s venom?

the polypetide toxins: acyl polyamine

Answer 6

1. toxins are voltage dependent open channel blockers/ blocker of ion channels with glutamate receptors
2. inhibit the channels -> inhibit depolarization -> no action potential -> induce paralysis

Question 7

what is in bee’s venom?

Answer 7

most commonly the apis melifera and apis melifera adansonii
venom consist of:
- melittin
- apamine -> blocker of Ca dependent K channles (can lead to death)
- mast cell degranulating peptide
- phospholipase A2 and B
- hyaluronidase
- histamine
- dopamine
- monosaccharides
- lipids and others

Question 8

toxicity mechanism of bee venom?

Answer 8

1. normally, high concentration of Ca will open K channels, increase effluc of K -> cause hyperpolarization
2. apamine block the channels, Ca is not used
3. accumulation of Ca lead to overstimulatin and over contraction of smooth muscles (inside vessels)
4. will increase blood pressure -> can lead to death, if fatal